HID Sensor Usage Tables - USB.org

61 HID Sensor Usages
Third 0x30 – 0x3f
Table 7. A Report ID allocation scheme example
Because the SETUP packet has fields describing the request type separate from the Report ID, it is OK to
“re use” Report IDs for Input Reports, Output Reports, and Feature Reports. For example, a sensor can
have an Input Report with Report ID 0x01, an Output Report with Report ID 0x01, and a Feature Report
with Report ID 0x01. These are all separate Reports with different contents. If you find this too confusing,
you may wish to assign different Report IDs, for example: an Input Report with Report ID 0x01, an Output
Report with Report ID 0x02, and a Feature Report with Report ID 0x03. Either technique is allowed.
If there is only one logical device, and that device only has a single Input Report, Output Report, and/or
Feature Report, then the Report ID is not mandatory and must be filled with the special value zero.
3.6 HID Report Items
Each report may incorporate one or more pieces of data, called Items. The Items always follow the Report
ID byte, i.e., the Items start at byte position 1 and work upward.
See Also
For more information about HID Report Items; please refer to Sections 5.2 and 5.3 of the Device Class
Definition for Human Interface Devices specification (Reference Document [2]).
Input Reports are sent from the device to the host. Input Reports may be sent “asynchronously” by the
device to the host (in actuality, the host bus controller periodically polls for these). The host may also
“demand” an Input Report by invoking a HID GET INPUT REPORT request. Sensor Data Fields, i.e.,
real-time acquired sensor data samples, are equated to HID Input Report Items.
Output Reports are sent from the host to the device. Output Reports are optional. In the context of
Sensors, Output Reports may be used to send functional commands to the Sensor by invoking the HID SET
OUTPUT REPORT request. In practice, configuration of sensors is more commonly done using the HID
SET FEATURE REPORT request instead.
See Also
For more information about HID Output Reports that may optionally be supported by some sensor device
implementations; please refer to the Device Class Definition for Physical Interface Devices (PID)
specification (Reference Document [7]). In that document, it describes how various types of Output
Reports could be used for advanced features such as downloading detailed Haptic feedback waveforms,
waveform shape “envelopes”, and “condition” definitions that can be used as complex triggers. Please note
that PID Usages appear on Usage Page 0x0F, not the Sensor Usage Page 0x20.
Feature Reports can be used to transfer non-real-time Properties between the device and the host. They are
optional, meaning that it is possible to define a sensor collection that communicates solely with Input
Reports. Feature Reports are also bi-directional, and sub-divided into Get Feature Reports and Set Feature
Reports, depending upon direction.
Get Feature Reports are sent from the device to the host. They are used to get Properties from a sensor by
invoking the HID GET FEATURE REPORT request. This might include identifying information such as
the sensor’s manufacturer and model number, or reading back previously set configuration settings. Sensor
Properties are equated to HID Feature Report Items.